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  <h1>Source code for torch.utils.data._utils.worker</h1><div class="highlight"><pre>
<span></span><span class="sa">r</span><span class="sd">&quot;&quot;&quot;&quot;Contains definitions of the methods used by the _BaseDataLoaderIter workers.</span>

<span class="sd">These **needs** to be in global scope since Py2 doesn&#39;t support serializing</span>
<span class="sd">static methods.</span>
<span class="sd">&quot;&quot;&quot;</span>

<span class="kn">import</span> <span class="nn">torch</span>
<span class="kn">import</span> <span class="nn">random</span>
<span class="kn">import</span> <span class="nn">os</span>
<span class="kn">from</span> <span class="nn">collections</span> <span class="kn">import</span> <span class="n">namedtuple</span>
<span class="kn">from</span> <span class="nn">torch._six</span> <span class="kn">import</span> <span class="n">queue</span>
<span class="kn">from</span> <span class="nn">torch._utils</span> <span class="kn">import</span> <span class="n">ExceptionWrapper</span>
<span class="kn">from</span> <span class="nn">.</span> <span class="kn">import</span> <span class="n">signal_handling</span><span class="p">,</span> <span class="n">MP_STATUS_CHECK_INTERVAL</span><span class="p">,</span> <span class="n">IS_WINDOWS</span>

<span class="k">if</span> <span class="n">IS_WINDOWS</span><span class="p">:</span>
    <span class="kn">import</span> <span class="nn">ctypes</span>
    <span class="kn">from</span> <span class="nn">ctypes.wintypes</span> <span class="kn">import</span> <span class="n">DWORD</span><span class="p">,</span> <span class="n">BOOL</span><span class="p">,</span> <span class="n">HANDLE</span>

    <span class="c1"># On Windows, the parent ID of the worker process remains unchanged when the manager process</span>
    <span class="c1"># is gone, and the only way to check it through OS is to let the worker have a process handle</span>
    <span class="c1"># of the manager and ask if the process status has changed.</span>
    <span class="k">class</span> <span class="nc">ManagerWatchdog</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
        <span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">manager_pid</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">getppid</span><span class="p">()</span>

            <span class="bp">self</span><span class="o">.</span><span class="n">kernel32</span> <span class="o">=</span> <span class="n">ctypes</span><span class="o">.</span><span class="n">WinDLL</span><span class="p">(</span><span class="s1">&#39;kernel32&#39;</span><span class="p">,</span> <span class="n">use_last_error</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">kernel32</span><span class="o">.</span><span class="n">OpenProcess</span><span class="o">.</span><span class="n">argtypes</span> <span class="o">=</span> <span class="p">(</span><span class="n">DWORD</span><span class="p">,</span> <span class="n">BOOL</span><span class="p">,</span> <span class="n">DWORD</span><span class="p">)</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">kernel32</span><span class="o">.</span><span class="n">OpenProcess</span><span class="o">.</span><span class="n">restype</span> <span class="o">=</span> <span class="n">HANDLE</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">kernel32</span><span class="o">.</span><span class="n">WaitForSingleObject</span><span class="o">.</span><span class="n">argtypes</span> <span class="o">=</span> <span class="p">(</span><span class="n">HANDLE</span><span class="p">,</span> <span class="n">DWORD</span><span class="p">)</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">kernel32</span><span class="o">.</span><span class="n">WaitForSingleObject</span><span class="o">.</span><span class="n">restype</span> <span class="o">=</span> <span class="n">DWORD</span>

            <span class="c1"># Value obtained from https://msdn.microsoft.com/en-us/library/ms684880.aspx</span>
            <span class="n">SYNCHRONIZE</span> <span class="o">=</span> <span class="mh">0x00100000</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">manager_handle</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">kernel32</span><span class="o">.</span><span class="n">OpenProcess</span><span class="p">(</span><span class="n">SYNCHRONIZE</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">manager_pid</span><span class="p">)</span>

            <span class="k">if</span> <span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">manager_handle</span><span class="p">:</span>
                <span class="k">raise</span> <span class="n">ctypes</span><span class="o">.</span><span class="n">WinError</span><span class="p">(</span><span class="n">ctypes</span><span class="o">.</span><span class="n">get_last_error</span><span class="p">())</span>

            <span class="bp">self</span><span class="o">.</span><span class="n">manager_dead</span> <span class="o">=</span> <span class="kc">False</span>

        <span class="k">def</span> <span class="nf">is_alive</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
            <span class="k">if</span> <span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">manager_dead</span><span class="p">:</span>
                <span class="c1"># Value obtained from https://msdn.microsoft.com/en-us/library/windows/desktop/ms687032.aspx</span>
                <span class="bp">self</span><span class="o">.</span><span class="n">manager_dead</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">kernel32</span><span class="o">.</span><span class="n">WaitForSingleObject</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">manager_handle</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span> <span class="o">==</span> <span class="mi">0</span>
            <span class="k">return</span> <span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">manager_dead</span>
<span class="k">else</span><span class="p">:</span>
    <span class="k">class</span> <span class="nc">ManagerWatchdog</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
        <span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">manager_pid</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">getppid</span><span class="p">()</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">manager_dead</span> <span class="o">=</span> <span class="kc">False</span>

        <span class="k">def</span> <span class="nf">is_alive</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
            <span class="k">if</span> <span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">manager_dead</span><span class="p">:</span>
                <span class="bp">self</span><span class="o">.</span><span class="n">manager_dead</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">getppid</span><span class="p">()</span> <span class="o">!=</span> <span class="bp">self</span><span class="o">.</span><span class="n">manager_pid</span>
            <span class="k">return</span> <span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">manager_dead</span>

<span class="n">_worker_info</span> <span class="o">=</span> <span class="kc">None</span>


<span class="k">class</span> <span class="nc">WorkerInfo</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
    <span class="n">__initialized</span> <span class="o">=</span> <span class="kc">False</span>

    <span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
        <span class="k">for</span> <span class="n">k</span><span class="p">,</span> <span class="n">v</span> <span class="ow">in</span> <span class="n">kwargs</span><span class="o">.</span><span class="n">items</span><span class="p">():</span>
            <span class="nb">setattr</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">k</span><span class="p">,</span> <span class="n">v</span><span class="p">)</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">__initialized</span> <span class="o">=</span> <span class="kc">True</span>

    <span class="k">def</span> <span class="fm">__setattr__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">key</span><span class="p">,</span> <span class="n">val</span><span class="p">):</span>
        <span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">__initialized</span><span class="p">:</span>
            <span class="k">raise</span> <span class="ne">RuntimeError</span><span class="p">(</span><span class="s2">&quot;Cannot assign attributes to </span><span class="si">{}</span><span class="s2"> objects&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="vm">__class__</span><span class="o">.</span><span class="vm">__name__</span><span class="p">))</span>
        <span class="k">return</span> <span class="nb">super</span><span class="p">(</span><span class="n">WorkerInfo</span><span class="p">,</span> <span class="bp">self</span><span class="p">)</span><span class="o">.</span><span class="fm">__setattr__</span><span class="p">(</span><span class="n">key</span><span class="p">,</span> <span class="n">val</span><span class="p">)</span>


<div class="viewcode-block" id="get_worker_info"><a class="viewcode-back" href="../../../../../data.html#torch.utils.data.get_worker_info">[docs]</a><span class="k">def</span> <span class="nf">get_worker_info</span><span class="p">():</span>
    <span class="sa">r</span><span class="sd">&quot;&quot;&quot;Returns the information about the current</span>
<span class="sd">    :class:`~torch.utils.data.DataLoader` iterator worker process.</span>

<span class="sd">    When called in a worker, this returns an object guaranteed to have the</span>
<span class="sd">    following attributes:</span>

<span class="sd">    * :attr:`id`: the current worker id.</span>
<span class="sd">    * :attr:`num_workers`: the total number of workers.</span>
<span class="sd">    * :attr:`seed`: the random seed set for the current worker. This value is</span>
<span class="sd">      determined by main process RNG and the worker id. See</span>
<span class="sd">      :class:`~torch.utils.data.DataLoader`&#39;s documentation for more details.</span>
<span class="sd">    * :attr:`dataset`: the copy of the dataset object in **this** process. Note</span>
<span class="sd">      that this will be a different object in a different process than the one</span>
<span class="sd">      in the main process.</span>

<span class="sd">    When called in the main process, this returns ``None``.</span>

<span class="sd">    .. note::</span>
<span class="sd">       When used in a :attr:`worker_init_fn` passed over to</span>
<span class="sd">       :class:`~torch.utils.data.DataLoader`, this method can be useful to</span>
<span class="sd">       set up each worker process differently, for instance, using ``worker_id``</span>
<span class="sd">       to configure the ``dataset`` object to only read a specific fraction of a</span>
<span class="sd">       sharded dataset, or use ``seed`` to seed other libraries used in dataset</span>
<span class="sd">       code (e.g., NumPy).</span>
<span class="sd">    &quot;&quot;&quot;</span>
    <span class="k">return</span> <span class="n">_worker_info</span></div>


<span class="sa">r</span><span class="sd">&quot;&quot;&quot;Dummy class used to signal the end of an IterableDataset&quot;&quot;&quot;</span>
<span class="n">_IterableDatasetStopIteration</span> <span class="o">=</span> <span class="n">namedtuple</span><span class="p">(</span><span class="s1">&#39;_IterableDatasetStopIteration&#39;</span><span class="p">,</span> <span class="p">[</span><span class="s1">&#39;worker_id&#39;</span><span class="p">])</span>


<span class="k">def</span> <span class="nf">_worker_loop</span><span class="p">(</span><span class="n">dataset_kind</span><span class="p">,</span> <span class="n">dataset</span><span class="p">,</span> <span class="n">index_queue</span><span class="p">,</span> <span class="n">data_queue</span><span class="p">,</span> <span class="n">done_event</span><span class="p">,</span>
                 <span class="n">auto_collation</span><span class="p">,</span> <span class="n">collate_fn</span><span class="p">,</span> <span class="n">drop_last</span><span class="p">,</span> <span class="n">seed</span><span class="p">,</span> <span class="n">init_fn</span><span class="p">,</span> <span class="n">worker_id</span><span class="p">,</span>
                 <span class="n">num_workers</span><span class="p">):</span>
    <span class="c1"># See NOTE [ Data Loader Multiprocessing Shutdown Logic ] for details on the</span>
    <span class="c1"># logic of this function.</span>

    <span class="k">try</span><span class="p">:</span>
        <span class="c1"># Initialize C side signal handlers for SIGBUS and SIGSEGV. Python signal</span>
        <span class="c1"># module&#39;s handlers are executed after Python returns from C low-level</span>
        <span class="c1"># handlers, likely when the same fatal signal had already happened</span>
        <span class="c1"># again.</span>
        <span class="c1"># https://docs.python.org/3/library/signal.html#execution-of-python-signal-handlers</span>
        <span class="n">signal_handling</span><span class="o">.</span><span class="n">_set_worker_signal_handlers</span><span class="p">()</span>

        <span class="n">torch</span><span class="o">.</span><span class="n">set_num_threads</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
        <span class="n">random</span><span class="o">.</span><span class="n">seed</span><span class="p">(</span><span class="n">seed</span><span class="p">)</span>
        <span class="n">torch</span><span class="o">.</span><span class="n">manual_seed</span><span class="p">(</span><span class="n">seed</span><span class="p">)</span>

        <span class="k">global</span> <span class="n">_worker_info</span>
        <span class="n">_worker_info</span> <span class="o">=</span> <span class="n">WorkerInfo</span><span class="p">(</span><span class="nb">id</span><span class="o">=</span><span class="n">worker_id</span><span class="p">,</span> <span class="n">num_workers</span><span class="o">=</span><span class="n">num_workers</span><span class="p">,</span>
                                  <span class="n">seed</span><span class="o">=</span><span class="n">seed</span><span class="p">,</span> <span class="n">dataset</span><span class="o">=</span><span class="n">dataset</span><span class="p">)</span>

        <span class="kn">from</span> <span class="nn">torch.utils.data</span> <span class="kn">import</span> <span class="n">_DatasetKind</span>

        <span class="n">init_exception</span> <span class="o">=</span> <span class="kc">None</span>

        <span class="k">try</span><span class="p">:</span>
            <span class="k">if</span> <span class="n">init_fn</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span><span class="p">:</span>
                <span class="n">init_fn</span><span class="p">(</span><span class="n">worker_id</span><span class="p">)</span>

            <span class="n">fetcher</span> <span class="o">=</span> <span class="n">_DatasetKind</span><span class="o">.</span><span class="n">create_fetcher</span><span class="p">(</span><span class="n">dataset_kind</span><span class="p">,</span> <span class="n">dataset</span><span class="p">,</span> <span class="n">auto_collation</span><span class="p">,</span> <span class="n">collate_fn</span><span class="p">,</span> <span class="n">drop_last</span><span class="p">)</span>
        <span class="k">except</span> <span class="ne">Exception</span><span class="p">:</span>
            <span class="n">init_exception</span> <span class="o">=</span> <span class="n">ExceptionWrapper</span><span class="p">(</span>
                <span class="n">where</span><span class="o">=</span><span class="s2">&quot;in DataLoader worker process </span><span class="si">{}</span><span class="s2">&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">worker_id</span><span class="p">))</span>

        <span class="c1"># When using Iterable mode, some worker can exit earlier than others due</span>
        <span class="c1"># to the IterableDataset behaving differently for different workers.</span>
        <span class="c1"># When such things happen, an `_IterableDatasetStopIteration` object is</span>
        <span class="c1"># sent over to the main process with the ID of this worker, so that the</span>
        <span class="c1"># main process won&#39;t send more tasks to this worker, and will send</span>
        <span class="c1"># `None` to this worker to properly exit it.</span>
        <span class="c1">#</span>
        <span class="c1"># Note that we cannot set `done_event` from a worker as it is shared</span>
        <span class="c1"># among all processes. Instead, we set the `iteration_end` flag to</span>
        <span class="c1"># signify that the iterator is exhausted. When either `done_event` or</span>
        <span class="c1"># `iteration_end` is set, we skip all processing step and just wait for</span>
        <span class="c1"># `None`.</span>
        <span class="n">iteration_end</span> <span class="o">=</span> <span class="kc">False</span>

        <span class="n">watchdog</span> <span class="o">=</span> <span class="n">ManagerWatchdog</span><span class="p">()</span>

        <span class="k">while</span> <span class="n">watchdog</span><span class="o">.</span><span class="n">is_alive</span><span class="p">():</span>
            <span class="k">try</span><span class="p">:</span>
                <span class="n">r</span> <span class="o">=</span> <span class="n">index_queue</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">timeout</span><span class="o">=</span><span class="n">MP_STATUS_CHECK_INTERVAL</span><span class="p">)</span>
            <span class="k">except</span> <span class="n">queue</span><span class="o">.</span><span class="n">Empty</span><span class="p">:</span>
                <span class="k">continue</span>
            <span class="k">if</span> <span class="n">r</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
                <span class="c1"># Received the final signal</span>
                <span class="k">assert</span> <span class="n">done_event</span><span class="o">.</span><span class="n">is_set</span><span class="p">()</span> <span class="ow">or</span> <span class="n">iteration_end</span>
                <span class="k">break</span>
            <span class="k">elif</span> <span class="n">done_event</span><span class="o">.</span><span class="n">is_set</span><span class="p">()</span> <span class="ow">or</span> <span class="n">iteration_end</span><span class="p">:</span>
                <span class="c1"># `done_event` is set. But I haven&#39;t received the final signal</span>
                <span class="c1"># (None) yet. I will keep continuing until get it, and skip the</span>
                <span class="c1"># processing steps.</span>
                <span class="k">continue</span>
            <span class="n">idx</span><span class="p">,</span> <span class="n">index</span> <span class="o">=</span> <span class="n">r</span>
            <span class="k">if</span> <span class="n">init_exception</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span><span class="p">:</span>
                <span class="n">data</span> <span class="o">=</span> <span class="n">init_exception</span>
                <span class="n">init_exception</span> <span class="o">=</span> <span class="kc">None</span>
            <span class="k">else</span><span class="p">:</span>
                <span class="k">try</span><span class="p">:</span>
                    <span class="n">data</span> <span class="o">=</span> <span class="n">fetcher</span><span class="o">.</span><span class="n">fetch</span><span class="p">(</span><span class="n">index</span><span class="p">)</span>
                <span class="k">except</span> <span class="ne">Exception</span> <span class="k">as</span> <span class="n">e</span><span class="p">:</span>
                    <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">e</span><span class="p">,</span> <span class="ne">StopIteration</span><span class="p">)</span> <span class="ow">and</span> <span class="n">dataset_kind</span> <span class="o">==</span> <span class="n">_DatasetKind</span><span class="o">.</span><span class="n">Iterable</span><span class="p">:</span>
                        <span class="n">data</span> <span class="o">=</span> <span class="n">_IterableDatasetStopIteration</span><span class="p">(</span><span class="n">worker_id</span><span class="p">)</span>
                        <span class="c1"># Set `iteration_end`</span>
                        <span class="c1">#   (1) to save future `next(...)` calls, and</span>
                        <span class="c1">#   (2) to avoid sending multiple `_IterableDatasetStopIteration`s.</span>
                        <span class="n">iteration_end</span> <span class="o">=</span> <span class="kc">True</span>
                    <span class="k">else</span><span class="p">:</span>
                        <span class="c1"># It is important that we don&#39;t store exc_info in a variable.</span>
                        <span class="c1"># `ExceptionWrapper` does the correct thing.</span>
                        <span class="c1"># See NOTE [ Python Traceback Reference Cycle Problem ]</span>
                        <span class="n">data</span> <span class="o">=</span> <span class="n">ExceptionWrapper</span><span class="p">(</span>
                            <span class="n">where</span><span class="o">=</span><span class="s2">&quot;in DataLoader worker process </span><span class="si">{}</span><span class="s2">&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">worker_id</span><span class="p">))</span>
            <span class="n">data_queue</span><span class="o">.</span><span class="n">put</span><span class="p">((</span><span class="n">idx</span><span class="p">,</span> <span class="n">data</span><span class="p">))</span>
            <span class="k">del</span> <span class="n">data</span><span class="p">,</span> <span class="n">idx</span><span class="p">,</span> <span class="n">index</span><span class="p">,</span> <span class="n">r</span>  <span class="c1"># save memory</span>
    <span class="k">except</span> <span class="ne">KeyboardInterrupt</span><span class="p">:</span>
        <span class="c1"># Main process will raise KeyboardInterrupt anyways.</span>
        <span class="k">pass</span>
    <span class="k">if</span> <span class="n">done_event</span><span class="o">.</span><span class="n">is_set</span><span class="p">():</span>
        <span class="n">data_queue</span><span class="o">.</span><span class="n">cancel_join_thread</span><span class="p">()</span>
        <span class="n">data_queue</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</pre></div>

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